Recently, in order to meet demands for high-speed and high-integration semiconductor devices having highly miniaturized wiring patterns, inter-wiring capacitance needs to be reduced while wiring conductivity and electromigration tolerance need to be improved. For the purpose, copper (Cu) having high electromigration tolerance and higher conductivity than that of conventionally used aluminum (Al) or tungsten (W) has been used as a wiring material. Widely used as a technique for forming a Cu wiring is a damascene process that involves previously forming wiring trenches or connection holes in an interlayer insulating film or the like and then burying Cu in the wiring trenches or the connection holes (see, for example, Patent Document 1).
Meanwhile, along with the miniaturization of the semiconductor devices, a parasitic capacitance of an interlayer insulating film becomes an important factor in improving wiring performance, and a low dielectric constant film (low-k film) made of a low dielectric constant material is used as an interlayer insulating film. As a material of the low-k film, a material having an alkyl group such as a methyl group as an end group is generally utilized.
However, in the above-mentioned conventional damascene process, the low-k film is damaged during an etching process or a resist film removing (asking) process. Such damage causes an increase of a dielectric constant of the low-k film, resulting in diminishment of an effect of using the low-k film as the interlayer insulating film.
As a technique for recovering such damage, Patent Document 2 discloses a recovery process using a silylizing agent is performed after the etching or the resist film removing process is carried out. In the recovery process, a methyl-group-containing gas such as the silylizing agent modifies a surface of a damaged layer of which the end group becomes a —OH group by a damage inflicted thereon, so that the end group becomes a methyl group or a group containing a methyl-group.
Since the processing gas such as the silylizing agent for use in performing such a recovery process is usually of a high price, it has been attempted to minimize a usage of the processing gas by diluting the processing gas with a dilution gas such as a N2 gas.
Patent Document 1: Japanese Patent Laid-open Publication No. 2002-083869
Patent Document 2: Japanese Patent Laid-open Publication No. 2006-049798
However, if a main processing gas diluted with the dilution gas is introduced into a chamber, a sufficient recovery process may not be achieved due to a reduced concentration of the processing gas and a reduced reaction by the dilution of the processing gas. Moreover, such a recovery process is performed while a semiconductor wafer (hereinafter, simply referred to as a wafer) having a low-k film is heated by a heater installed in a mounting table after the wafer is mounted on the mounting table. Since the inside of the chamber is in a depressurized state, it takes time until the wafer reaches a preset processing temperature. Thus, if the processing gas diluted with the dilution gas is introduced into the chamber, the introduced processing gas would remain unnecessary until the wafer reaches the processing temperature.